Multiple blood bags are commercially available from the Fenwal Division of Baxter Travenol Laboratories, Inc., for collecting and processing blood under sterile conditions to obtain various blood components as may be desired, for example, packed red cells, plasma, platelets, and cryoprecipitate.
The currently-available blood bags are made of a polyvinyl chloride formulation, which includes, as an ester-type plasticizer, di-2-ethylhexylphthalate. This blood bag system has served extremely well in the storage and processing of blood and blood components, exhibiting a high survival rate, with a resultingly low plasma hemoglobin content after, for example, 21 days of storage.
However, some concern has been expressed from various sources about the potential undesirability of the plasticizer leaching from the plastic material, and entering the blood, from where it is infused to the patient upon infusion of the blood or blood components. This is so despite the lack of any apparent significant toxicity of the particular plasticizer used, the concern being about long-term and subtle effects not yet discovered.
Accordingly, various plastic formulations which are flexible, translucent, sterilizable, and free of liquid plasticizers capable of leaching have been tested as blood bag materials. Many of the plastic formulations which have been tested have physical characteristics which are different from each other and from the current polyvinyl chloride formulations. For example, some plastic formulations have an improved capacity to transfer carbon dioxide, so that it would be of advantage to make one or more of the transfer packs of a multiple blood bag of such a material to permit an increased diffusion rate of carbon dioxide through the transfer pack during platelet storage so that the pH decrease of the platelets during storage is reduced.
It has been surprisingly found that the presence of certain ester-type plasticizers such as di-2-ethylhexylphthalate and di-2-ethylhexyladipate in plastics causes a significant lowering of the plasma hemoglobin content during long-term storage of blood in containers made of such plastics.
Accordingly, in accordance with this invention, the overall contact of blood plasma and other components to the blood-extractable plasticizer may be minimized, while still attaining low plasma hemoglobin levels in long-term storage, by providing a multiple blood bag system in which the donor bag is made of a plastic which contains a blood extractable plasticizer, preferably a branched dioctyl phthalate ester plasticizer, but the transfer bags are free of blood extractable plasticizers. Accordingly, the red blood cells, which normally are retained in the donor bag, are stabilized and preserved by the surprising benefit which has been found by the presence of the specific plasticizers described above. At the same time, the plasma and other blood components may be removed from the donor bag, being thus freed from further exposure to the plasticizer, and stored in transfer bags of different materials of different desirable characteristics, for example, transfer bags made of a material having relatively high carbon dioxide diffusion capability.
Accordingly, in accordance with this invention, the specific properties of the various bags of the multiple blood bag of this invention may be optimized by the use of different materials for each of the bags as desired, with one bag material being chosen for the donor bag in order to minimize the formation of plasma hemoglobin and to maximize the life of the red cells, while the transfer packs may be made of material having other characteristics, for example, the relatively high carbon dioxide diffusion capability.